1417 patients ≥ 18 years of age (mean 53 y, 62% women) who presented with signs and symptoms of acute PE, with or without signs of deep venous thrombosis (DVT); and were assessed to be clinically likely (Wells model score ≥ 4.5) or unlikely (score < 4.5) to have PE but with a positive D-dimer test. Exclusion criteria included PE or DVT in the past 3 months; unchanged pulmonary symptoms in the past 2 weeks; need for long-term anticoagulants; use of therapeutic doses of parenteral anticoagulants for > 48 hours; life expectancy < 3 months; contraindication to contrast media; and pregnancy.

Intervention

Initial diagnostic imaging with CTPA (n = 701) or V/Q scan (n = 716). CTPA was done with either single (n= 195) or multidetector (n= 499) systems. Patients with positive CTPA or high-probability V/Q scans were considered to have PE; patients with normal V/Q scans were considered to have PE excluded. All other patients had leg ultrasonography (US). Management was based on clinical likelihood of PE, D-dimer, and US results. Patients diagnosed with PE or DVT were anticoagulated.

Outcomes

Development of DVT or PE at 3 months in patients in whom PE had initially been ruled out; and death.

Patient follow-up

99% (intention-to-treat analysis).

Main results

In the initial diagnostic period, 234 patients (17%) were diagnosed with PE or DVT. Among the 1172 patients in whom venous thromboembolism (VTE) was initially excluded as a diagnosis, the CTPA and V/Q groups did not differ for VTE at 3 months (Table); the between-group difference of −0.6% (95% CI −1.6 to 0.3) met the prespecified criteria for noninferiority (i.e., < 2.5% absolute difference between groups). The groups did not differ for mortality (Table).

Conclusion

Computed tomographic pulmonary angiography was not inferior to ventilation–perfusion lung scanning as part of a diagnostic-management strategy for ruling out pulmonary embolism.

†DVT = deep venous thrombosis; NS = not significant; other abbreviations defined in Glossary. RRR, NNT, and CI calculated from data in article. Analysis based on 1172 patients in whom PE was ruled out during initial testing.